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Zermelo-Fraenkel set theory
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Singleton map
Formulation 0
Let $X$ and $Y$ each be a
D11: Set
such that
(i)
\begin{equation} \{ \{ x \} : x \in X \} \subseteq Y \end{equation}
The
singleton map
from $X$ to $Y$ is the
D18: Map
\begin{equation} X \to Y, \quad x \mapsto \{ x \} \end{equation}
Child definitions
»
D4493: Canonical singleton map